1. Technical Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to a semiconductor device having an interlayer insulation film having a lower dielectric constant than that of SiO2 and the method of manufacturing the same.
2. Description of the Related Art
To accomplish high speed and high integration of LSI, delay of a signal transmission speed caused by an electric capacity between wirings and between interlayer insulation films has been a problem. In this regard, particularly in recent years, studies aiming for a low dielectric constant of an interlayer insulation film have progressed, and for example, organic compounds such as polyimide polymer, bisbenzocyclobutene siloxane polymer (hereinafter referred to as xe2x80x9cBCBxe2x80x9d) are used as an interlayer insulation film. A specific dielectric constant of such organic compounds is about 1.5 to 2.5, and is greatly lower than that (about 4) of the conventional interlayer insulation film mainly formed of SiO2. In addition, it is possible that these organic compounds are easily deposited by spin coating and sintering and are deposited flat regardless of undulation of a base structure.
However, in the case of forming an interlayer insulation film by the organic compounds, adherence to a metal used in wiring is weak, and the exfoliation tends to occur. Thus, in order to improve the adherence, an interlayer adhesion layer has been provided between the interlayer insulation film by the organic compounds and the wiring. For example, in case of using BCB as an interlayer insulation film, SiN and the like are used as an interlayer adhesion layer. Hereinafter, using this embodiment, a structure of a semiconductor device will be explained with the manufacturing method thereof.
FIG. 1 is a cross sectional view showing GaAs-IC using BCB as an interlayer insulation film, in method of manufacturing the GaAs-IC, first, a first metal wiring 102 formed of Au, etc. and including a device section such as FET is formed on a GaAs substrate 101 by sputtering method and dry etching method. Next, a first interlayer adhesion layer 103 formed of SiN is formed, for example, by plasma CVD method, etc. However, the first interlayer adhesion layer 103 can be omitted in case where sufficient adherence is obtained between the first metal wiring 102 and an interlayer insulation film 104 explained later.
Next, the interlayer insulation film 104 is formed of BCB and in the thickness of 1,000 to 20,000 nm, for instance, by the steps of coating BCB in a desired thickness, and then, sintering and hardening the BCB under N2 atmosphere at a temperature of 300xc2x0 C. Then, a second interlayer adhesion layer 106 is formed of SiN by plasma CVD method. Next, a through hole 110 is formed by means of dry etching using a photoresist mask (not shown). For example, SiN is etched by RIE using a mixed gas of CF4 and H2, and BCB is etched by RIE using a mixed gas of CF4 and O2. After that, a second metal wiring 108 formed of Au, etc. is formed by sputtering method, etc. Also, a protection layer (not shown) is formed to protect the second metal wiring 108. The protection layer is formed of SiN and the like, which have excellent adherence to the second metal wiring 108.
In addition, if the thickness of the SiN layer used in the interlayer adhesion layer 103 and the protection layer 109 is thick, it causes the specific dielectric constant to rise, thereby, it is desirable to form the SiN layer to be about 50 to 100 nm as thin as possible.
By the above-mentioned structure, an interlayer insulation film in a semiconductor device can accomplish a low dielectric constant while maintaining excellent adherence to a metal wiring. However, there is a big difference in a mechanical characteristic between the organic compound used as an interlayer insulation film and a material such as SiN used as an interlayer adhesion layer. For example, regarding an interlayer insulation film of 5 xcexcm in thickness using BCB and an interlayer adhesion layer of 0.3 xcexcm in thickness using SiN, the stress and elastic modulus thereof are shown in Table 1. In Table 1, a mark xe2x80x9c+xe2x80x9d and a mark xe2x80x9cxe2x88x92xe2x80x9d added to the numerical value indicate a tensile stress and a Compressive stress, respectively, and BCB and SiN have the tensile stress and the compressive stress, respectively. Also, there is a large difference in the elastic modulus between BCB and SiN. Accordingly, in case of stacking the both, a strong stress occurs in the interface between them, so that brittle fracture tends to occur in the SiN side having higher elastic modulus, and reliability of the semiconductor device is greatly damaged.
An object of the present invention is to provide a semiconductor device using an organic compound having a lower dielectric constant than that of SiO2 as an interlayer insulation film which has high reliability without fracture by stress concentration while maintaining adherence between said interlayer insulation film and the metal wiring and method of manufacturing the same.
According to one aspect of the present invention, there is provided a semiconductor device comprising: a first metal wiring; an interlayer insulation film formed on the metal wiring and formed of an organic compound having a lower dielectric constant than that of SiO2; a second metal wiring formed on said interlayer insulation film; an interlayer adhesion layer formed to improve adherence between said interlayer insulation film and said second metal wiring; and a stress buffer layer formed between said interlayer insulation film and said interlayer adhesion layer and having the elastic modulus higher than that of said interlayer insulation film and lower than that of said interlayer adhesion layer.
According to the semiconductor device of the present invention, it is preferred that said interlayer insulation film is formed of a bisbenzocyclobutene siloxane polymer and said interlayer adhesion layer is formed of SiN, said stress buffer layer being formed of SiO2, With this, in the semiconductor device using an organic compound as an interlayer insulation film, it is possible to prevent brittle fracture by the stress concentration while maintaining adherence between the metal wiring and the interlayer insulation film, so that reliability of the semiconductor device is improved.
According to another aspect of the present invention, there is provided a method of manufacturing a semiconductor device comprising the steps of: forming an interlayer adhesion layer on a first metal wiring; forming a stress buffer layer of which the elastic modulus is lower than that of said interlayer adhesion layer on said interlayer adhesion layer; forming an interlayer insulation film of which the elastic modulus is lower than that of said stress buffer layer and which is formed of an organic compound having a lower dielectric constant than that of SiO2 on said stress buffer layer; and forming a second metal wiring on said interlayer insulation film. With this, in the semiconductor device using an organic compound as an interlayer insulation film, it is possible to prevent brittle fracture by the stress concentration while maintaining adherence between the metal wiring and the interlayer insulation film, so that reliability of the semiconductor device is improved.
According to the method of manufacturing the semiconductor device of the present invention, it is preferred that said stress buffer layer is formed by any one of thermal CVD method, plasma CVD method and optical CVD method. With this, in the semiconductor device using an organic compound as an interlayer insulation film, it is possible to prevent brittle fracture by the stress concentration while maintaining adherence between the metal wiring and the interlayer insulation film, so that reliability of the semiconductor device is improved.
According to the method of manufacturing the semiconductor device of the present invention, it is preferred that said interlayer insulation film is a bisbenzocyclobutene siloxane polymer film formed by sequentially performing spin coating, and sintering and hardening steps and said interlayer adhesion layer is SiN film formed by any one of thermal CVD method, plasma CVD method and optical CVD method, said stress buffer layer being SiO2 film formed by any one of thermal CVD method, plasma CVD method and optical CVD method. With this, in the semiconductor device using an organic compound as an interlayer insulation film, it is possible to prevent brittle fracture by the stress concentration while maintaining adherence between the metal wiring and the interlayer insulation film, so that reliability of the semiconductor device is improved.